PostgreSQL backend storage insights

Dear all

I m quite new at HC Vault but I want to understand how HC Vault (1.7.1) works with PostgreSQL v.9.5 as backend storage (reference: PostgreSQL - Storage Backends - Configuration | Vault | HashiCorp Developer).
Is there any documentation about the tables vault_kv_store, vault_ha_locks and what kind of data are going to be stored in this table columns e.g. vault_kv_store.parent_path, vault_kv_store.path? Also I m using KV and Transit secret engine for encrytion/decryption.

Thank you for support.